Hello!
Our group has a question regarding the units of a PSD source map. We are working with resting-state MEG data. Our processing pipeline includes using the LCMV beamformer and calculating PSDs on those maps. We did not normalize these PSDs and are wondering what these units should be. When looking at the raw recordings the units are fT. However, the surface maps show "no units" under the color bar. What units are being displayed on this surface map?
Thank you!
The LCMV source model produces source time series that are unitless, because they correspond to standardized statistical fluctuations of neural currents. The resulting PSD is therefore unitless as well.
This information is now found in the: LCMV beamformer section of the source estimation tutorial.
Hey Natepetro!
I am working on resting state MEG data too. I want to use LCMV beamformer but not sure of what should the baseline be for the data covariance matrix computation. May I know, what time segment you considered for the baseline ?
Hello,
My apologies, I wasn’t tracking responses on this forum for some time. I assume you have already found an answer. But, in our case we are looking at resting state data and do not use a baseline. Typically, you will want your baseline to be of equal duration and bandwidth to the time/frequency window you beamform. And, its best to take a look at the spectrograms averaged across participants to choose a specific timewindow that does not contain lots of noise. Hope that helps.
thank you!!